method OutgoingMessage.prototype.appendHeader
Usage
import { OutgoingMessage } from "node:http";
Append a single header value for the header object.
If the value is an array, this is equivalent of calling this method multiple times.
If there were no previous value for the header, this is equivalent of calling outgoingMessage.setHeader(name, value).
Depending of the value of options.uniqueHeaders when the client request or the
server were created, this will end up in the header being sent multiple times or
a single time with values joined using ; .